With the arrival of Amazon's App Store, Android users have a new way to get their app and game fix. But while it is--overnight--the best known alternative app store, it's by no means the first. Third-party Android app stores such as AndAppStore, SlideMe, Handango, and GetJar and game developers such as Gameloft have been peddling their wares outside of the Android Market for some time now.

Additionally, smaller developers often offer alpha or beta versions of upcoming apps, while hackers and enthusiasts will sometimes make useful applets available to the Android community on forums and blogs. There are plenty of places to get your app fix outside of the official Android Market, but there's just one hoop you'll have to jump through first. Most Android devices don't allow the installation of apps from what Google refers to as "unknown sources."

Fortunately, it's usually very easy to enable this functionality. We outline the process in the video above, but here's the abridged version:

Simply pop over to your phone's Settings menu (usually found by hitting the menu button from the home screen) and tap the option for Applications.

You should see an option that says "Unknown sources." Fill the check box next to it, then click OK on the resulting popup alert.

You should now be able to install apps that you download from the Amazon App Store, from your alternative app store of choice, or from your favorite Android enthusiast forum. Amazon should handle the installation automatically, but from other sources you may have to download and launch the app's Android Package (APK) file yourself.

Unfortunately, not all Android devices will offer this option. Most notoriously, devices offered by wireless carrier AT&T have locked users out of enabling unknown sources. You can get around this restriction by rooting your phone, but that's the subject of another How to.